A thermodenuder is a device that enables the study of the volatility of engine combustion particles that are found in the exhaust of the engine. For example, aircraft engine exhaust is a complex mixture of gaseous molecules and ultrafine particulate matter. Depending on the combustion conditions and the fuel burned, large fractions of the materials present in the exhaust could be semi-volatile in nature. It is believed that condensation of semi-volatile species onto the particles is responsible for the formation of volatile particles in the exhaust plume downstream from the engine exhaust nozzle. Heavier polyaromatic hydrocarbons, for example, is one class of species that participates in the condensation. Fuel sulfur is another fuel constituent of volatile species in engine exhaust.